Compress MP3

Make MP3 files smaller by re-encoding them at a lower bitrate. Compress MP3 files here in your browser: choose 64, 96, 128 or 160 kbps, convert, and see each file's size before and after.

How it works

  1. 1.Add MP3 files

    Podcast episodes, lectures, voice recordings, music — up to 15 at once.

  2. 2.Pick a lower bitrate

    96 kbps is the default. Go down to 64 kbps for speech, or use 128–160 kbps for music.

  3. 3.Compress

    Each file is decoded and encoded again with LAME at the new bitrate, on your device.

  4. 4.Compare and download

    Every row shows the size before and after and the percentage saved. The new file gets a -compressed suffix, so it never overwrites the original.

Compression settings

  • Bitrate: 64, 96, 128 or 160 kbps, for the whole batch or per file.
  • Force mono folds stereo into one channel, which suits speech: the whole bitrate goes to a single channel.
  • Trim the start and end, and match loudness across files.
  • Tags such as title and artist stay on the file; embedded cover art is not carried over.

How MP3 size and quality trade off

An MP3's size is its bitrate times its length. A minute takes about 0.5 MB at 64 kbps, 0.7 MB at 96 kbps, 1 MB at 128 kbps and 1.2 MB at 160 kbps.

This MP3 file size reducer works by encoding again at a lower bitrate. That always costs some quality: what the first encode removed stays gone, and the second encode removes more.

Speech holds up well — podcasts, lectures and voice memos usually stay clear at 64 kbps (especially in mono) or 96 kbps. Music keeps more of its detail at 128 or 160 kbps.

If the source is already at or below the bitrate you pick, the file won't get smaller and may even grow. Pick a lower setting, or keep the original as it is.

Privacy and file limits

Compression runs in your browser with a WebAssembly build of FFmpeg and the LAME encoder. Your MP3s are not uploaded, so there is no waiting for a server and no copy left behind on one.

On a computer you can add up to 15 MP3 files at once, 200 MB each and 500 MB in total. Phones get 50 MB per file and 120 MB per batch, because a mobile tab has far less memory to work with.

Related converters

Starting from a WAV recording? Encode it straight to the size you want with WAV to MP3. Voice notes in .m4a or .opus go through M4A to MP3 and Opus to MP3 first.